The present invention relates to cryosurgical probes, and more particularly to a cryo-probe construction that provides rapid defrost of an ice ball that is formed during use of the probe for cell necrosis. Cryosurgical probes have been built that use direct expansion of liquid refrigerant R12, carbon dioxide, nitrous oxide and other materials having two phase characteristics in a desired temperature range. The mentioned materials, stored at room temperature can produce temperatures in a range from -29.degree. C. to -88.degree. C. for the purpose of killing tissue in surgical procedures. Liquid nitrogen has also been used as a refrigerant in probes. This refrigerant has a boiling point at atmospheric pressure of -196.degree. C. Some probes provide very small cold surfaces for surgical procedures in the eye, brain or heart, and other probes require larger surface areas, and more cooling power for operation on larger tissue volumes and areas.
These cryo-probes generally have at least two circuits, one for delivering refrigerant to the active or distal end of the probe where cryosurgery is performed, and the other circuit for returning refrigerant from the active cold end to a vent port. The refrigerant generally is a superheated vapor at discharge. Probes of the prior art differ from each other generally in the means that are employed to keep the outside surfaces of the cryo-probe warm, except for the active end, and in the means for warming the cryo-probe after the surgical procedure is completed. Rapid warming is especially important when an ice ball forms on the cold working end of the probe during surgery, and it is not possible to safely move or remove the probe until the probe is separated from the ice ball or the ball is melted.
It is desirable that the apparatus, i.e., the refrigerant supply and control system for a cryo-probe be located outside the sterile field where cryosurgery is performed. Accordingly, conduits of extended length are required between the control and supply apparatus and the probe itself. It is also desired that any vented refrigerant be disposed outside of the sterile field. These logistical matters must be accommodated with the least inconvenience and impediment to the surgeon. Thus, long, flexible and small gauge conduits are desirable between the supply and the probe.
Efficient use of refrigerant is also important so that local supplies of refrigerant are not quickly exhausted, and the need to complete surgery quickly because of limitations and availability of refrigerant, is eliminated as a major consideration for the surgeon.
In summary, what is needed is a cryo-probe of high performance capability that is easy and convenient for a surgeon to use during surgery.